Many dangerous diseases in humans and animals are known to be caused by microorganisms, such as bacteria and microfungi. Bacteria cause epidemic diseases such as cholera, typhoid fever, paratyphoid fever, plague, diphtheria, tularemia, brucellosis, as well as tuberculosis, septicemia (blood poisoning), leprosy, syphilis, and others. In animals, bacteria cause equinia, anthrax, tuberculosis, and other diseases. Fungal diseases mainly affect the skin and mucous membranes, particular examples being keratomycoses, microsporum, trichophytosis, and cryptococcosis.
Strategy in the fight against microorganisms involves the administration of antimicrobial agents, such as antibacterial agents (including antibiotics) and antifungal agents. However, many know agents suffer from drawbacks such as toxicity, sensitivity to proteolytic enzymes, a hemolytic effect, and an insufficient range of antimicrobial activity. In particular, bacteria rapidly develop resistance toward known antimicrobial agents, primarily antibiotics. In this context, a search for novel nontoxic and biocompatible antimicrobial agents that would not cause resistance is of great interest.
Hemin is known to have an antimicrobial activity against Staphylococcus aureus [Y. Nitzan, H. Ladan, S. Gozansky, and Z. Malik, “Characterization of Hemin Antibacterial Action on Staphylococcus aureus,” FEMS Microbiol. Lett., 1987, Vol. 48 (3), pp. 401-406]. However, the use of hemin as an antibacterial agent is hampered by its water insolubility, hemolytic activity, and short-term antibacterial effect.
Attempts have been undertaken at modifying hemin by conjugating it with amino acids and peptides with the aim of designing biologically active derivatives. As a result of modifying the carboxy groups of hemin by preparing the corresponding amides, compounds of general formula (I) have been prepared and characterized, wherein R1 and R2, the same or different, are —OH or an amino acid or peptide moiety, and wherein R1 and R2 cannot simultaneously be —OH.

Some peptide hemin derivatives of general formula (I), in particular those wherein one of R1 and R2 is —OH and the other is -ArgArgTrpHisArgLeuLysGlu(OMe)OH (SEQ ID NO:1, compound V), or -ArgTrpHisArgLeuLysGlu(OMe)OH (SEQ ID NO:2, compound VI), have been found to have a nuclease (nucleolytic) activity, which is manifested as the ability to destroy plasmid DNA [RU patent No. 2250906, Apr. 27, 2005; Zheltukhina, G. A., Lobanova, T. N., Nebolsin, V. E., Gallyamov, M. O., Dranitsyna, S. M. and Kostanyan, I. A., Bioorg. Khim., 2006, Vol. 32, No. 2, pp. 198-210].
Some amino acid and peptide hemin derivatives of general formula (I), namely, those wherein one of R1 and R2 is —OH and the other is -ArgArgTrpHisArgLeuLysGlu(OMe)OH (SEQ ID NO:1 compound V), or R1=R2=-ArgOMe (compound VII), are capable of inhibiting HIV proteinase and, as a result, exert an anti-HIV antiviral action [RU patent No. 2238950, Oct. 27, 2004].
Antiviral activity has been demonstrated for some hemin derivatives of general formula (I), namely, for those wherein R1=R2=-SerOMe (compound VIII), R1=R2=-βAlaHis (compound X), R1=R2=-ArgOMe (compound VII), R1=R2=-βAlaHA (compound IX, HA=histamine moiety), or wherein one of R1 and R2 is —OH and the other is -ArgArgTrpHisArgLeuLysGlu(OMe)OH (SEQ ID NO:1, compound V), or -ArgTrpHisArgLeuLysGlu(OMe)OH (SEQ ID NO:2, compound VI) [RU application No. 2007125604, Jan. 20, 2009].
The antimicrobial (specifically, antibacterial and antifungal) activity of the aforementioned hemin derivatives is, however, not known in the art.
On the other hand, a lot of attention has recently been paid to the design of novel antimicrobial agents based on antimicrobial peptides (AMPs) [A. Giuliani, G Pirri, and S. F. Nicoletto, “Antimicrobial Peptides: An Overview of a Promising Class of Therapeutics,” Central European Journal of Biology, 2007, Vol. 2 (1), pp. 1-33].
Of the known antimicrobial peptides, we can mention linear gramicidin D, which is a mixture of peptides of formula (II):Val-Gly-Ala-(D-Leu)-Ala-(D-Val)-Val-(D-Val)-Trp-(D-Leu)-X-(D-Leu)-Trp-(D-Leu)-TrpNHCH2CH2OH (SEQ ID NO:3)  (II)wherein X=Trp, Tyr, or Phe    [W. E. Herrell and D. Heilman, “Experimental and Clinical Studies on Gramicidin,” J. Clin. Invest., 1941, Vol. 20, pp. 583-591]; and cyclic gramicidin S of formula (III):
[G Nagamurthi and S. Rambhav, “Gramicidin-S: Structure—Activity Relationship,” J. Biosci., 1985, Vol. 7, Nos. 3-4, pp. 323-329].
Compound II is effective against Gram-positive bacteria [W. E. Herrell and D. Heilman, “Experimental and Clinical Studies on Gramicidin,” J. Clin. Invest., 1941, Vol. 20, No 583] and against some viruses, in particular herpes virus [U.S. Pat. No. 6,001,808, 1999]. Compound III is effective primarily against Gram-positive bacteria in concentrations of 5 to 15 μM [Jingbo Xiao, Bernard Weisblum, and Peter Wipf, “Electrostatic versus Steric Effects in Peptidomimicry: Synthesis and Secondary Structure Analysis of Gramicidin S Analogues with (E)-Alkene Peptide Isosteres,” J. Am. Chem. Soc., 2005, 127 (16), pp. 5742-5743]. Compounds II and III are used in medical practice only for topical applications. Drawbacks of these antimicrobial agents consist in their relatively long lengths and the associated relatively high costs; an insufficient range of antibacterial, antifungal, and antiviral effect; and side effects of their application, primarily hemolysis of erythrocytes and allergic reactions.
Further, there is an Arg-Gly-Asp peptide (IV), which is a fragment of cecropin family antimicrobial peptides, many microbial proteins, and mammal cell surface fibronectin [A. J. Kastin, “Handbook of Biologically Active Peptides,” Elsevier/Academic Press, USA, 2006, p. 576]. However, its usefulness as an agent for the treatment of infectious diseases has not yet been studied.
The main obstacles to the use of AMPs in clinical practice consist of their relatively high costs, susceptibility to proteolytic enzymes, and the hemolytic effect intrinsic to many AMPs.
In addition, the major pathway to produce antimicrobial peptides is currently a solid-phase method, which makes them very expensive and their use uneconomical. Therefore, a search for shorter analogues of AMPs and their derivatives, in particular, for conjugates with compounds of other classes, is of great interest.
In the context of the persistent need for improving antimicrobial agents as regards reducing the toxicity and other side effects thereof and for enhancing their activity against resistant strains, hemin derivatives have been proposed for use as such the agents.